Subsurface thermal storage also helps heat the Netherlands sustainably in the winter

KWR participates in a European consortium to demonstrate and optimise subsurface seasonal storage of sustainable heat

This week sees the start of the HEATSTORE project: a 16-million-euro European project aimed at making technologies for the subsurface seasonal storage of sustainable heat ready for market uptake. With 23 European parties from nine countries the deployment is Europe-wide. In six demonstration projects – in the Netherlands, Belgium, Germany, France and Switzerland – subsurface storage techniques will be researched with a view to making use in the winter of the surplus sustainable heat stored in the summer. HEATSTORE will focus particularly on the storage of geothermal heat, but also of heat from other sustainable sources, such as residual heat from industry.

HEATSTORE not only involves the demonstration and study of heat storage, it is also dedicated to the rapid transfer of the technologies to industry. Apart from the project coordinator ECN (now part of TNO), the other Dutch participants are the consultancy IF Technology, the energy company ECW, the water research institute KWR, and the Netherlands Institute of Ecology (NIOO-KNAW).

Figure 1: the famous heat bathtub: high demand for heat in the winter and low demand in the summer. Subsurface storage enables the optimal use of the heat surplus and supply from various sources (e.g., solar heat) in the summer.

Figure 1: the famous heat bathtub: high demand for heat in the winter and low demand in the summer. Subsurface storage enables the optimal use of the heat surplus and supply from various sources (e.g., solar heat) in the summer.

Larger-scale storage at higher temperatures

By smartly configuring heat sources and storage technologies it should be possible in the future to cover the needs of an entire season with the stored heat. In the Netherlands, heat is stored in the subsurface and in the winter fed into the heat networks. The practice of storing heat for later use therefore does exist, but not yet at the scale needed to meet the heating requirements at the neighbourhood, city or regional level sustainably. Such large-scale subsurface thermal storage would enable the optimal utilisation of sustainable sources like geothermal heat, industrial residual heat and power-2-heat from variable solar and wind energy, at a lower cost and with a minimal impact on surface space.

Preventing negative impact of storage

To realise the available potential, it is essential that subsurface thermal storage have no negative impact on other uses of the subsurface, such as drinking water production. This aspect is also part of HEATSTORE. KWR will be researching not only how to recover as much as possible of the stored heat, but also what determines the impact of the heat that does escape. To this end, for instance, there will be an expansion within HEATSTORE of the ongoing monitoring of the subsurface thermal storage occurring in the Koppert-Cress pilot.

Smarter heat networks with storage

The collaborating parties want to increase the storage temperature by between 25 and 90 degrees. This would also offer benefits in connecting the storage to a heat network. Heat can be stored in subsurface aquifers, borewells or empty mines. The project involves the demonstration of storage technologies in combination with a variety of heat sources: geothermal, solar and residual heat – for example, from waste processing. By smartly configuring the sources, users and storage in a heat network, the costs of the whole system could be radically reduced – the ambition is to achieve a cost reduction of at least 20%.

Stimulate industry

Large-scale subsurface thermal storage requires the combination of the expertise of research institutes and the participation of industry. HEATSTORE strives to transfer the techniques as fast as possible to industry, so that it can quickly start working with the results. Besides the further development of technology, the project is also directed at societal embedding, business-model research and the legal-regulatory framework.


HEATSTORE is one of the nine innovative geothermal energy projects being subsidised by the GEOTHERMICA – ERA NET COfund. GEOTHERMICA is a joint initiative of EU member states and associated countries for research and innovation activities, with supplementary financial support from the European Commission. GEOTHERMICA supports international innovation projects by publishing joint calls. GEOTHERMICA also conducts activities directed at improving the coordination between public research and innovation programmes in different countries, and at the better application of the results of the funded projects. represents the Netherlands with expertise and subsidy resources in GEOTHERMICA. The Dutch participation in the projects is financed through the Renewable Energy scheme.